In mechanical devices, such as pumps driven by a shaft connected to a motor or other means to move fluids, slurries, and the like, the shaft passes through a seal cavity, or a “stuffing box,” defined by a cylindrical cavity in the device housing. The shaft is supported by bearings at the motor end. A seal and packing rings are placed in the stuffing box to engage the shaft to prevent fluids and slurries from passing through the seal cavity and reaching the bearings and the motor, causing damage to both.
In fossil fuel burning power plants and similar boilers, soot deposits collect on the heat transfer pipes, and buildup of such deposits can seriously interfere with proper heat transfer efficiency. Such power plants and boilers are provided with sootblower assemblies to clean soot from the exterior of the heat transfer pipes. Such assemblies typically include an elongate hollow tubular lance which has steam or air discharge nozzles adjacent the leading end of the tubular lance, which tubular lance is moved inward into the heat transfer chamber in generally parallel relationship to one or more adjacent heat transfer pipes to eject steam or air against these pipes to dislodge the soot therefrom. The tubular lance in turn is rotatably and axially slidably supported on an elongated and cantilevered stationary steam supply pipe which projects coaxially into the tubular lance. A packing assembly cooperates between the tubular lance and a steam supply pipe to create a sealed relationship therebetween, while at the same time permitting the tubular lance to be axially and rotatably advanced into the heat exchange chamber when removal of soot is desired. Each power plant or boiler typically has a large number of such soot removal, or “sootblower”, devices. The tubular lance of each device must be cantilevered inwardly and moved a significant distance, perhaps as much as 40 feet.
In reciprocating pumps having a liquid end and a drive end, a fixed volume of fluid is displaced for each stroke of the drive end. The shaft driven by the drive end has only axial movement and generally operates at higher pressures than rotary pumps, sometimes up to about 10,000 psi. These high pressures present special problems for conventional flexible pump packings. Certain piston-driven valves operate in similar fashion and have similar concerns.
Thus, there is a need for sealing materials that provide an improved bearing surface and sealing environment for sootblowers, reciprocal pumps, piston valves, and other uses and that are chemically, mechanically, and thermally resistant. Accordingly, It is desirable to provide an improved shaft seal-bearing assembly for use in the seal cavity or stuffing box of sootblowers, reciprocal pumps, and piston valves to provide an improved bearing surface and seal.